Integral joint drill pipe



e 17, 1941- H. W.--'GRAHA'M 2,246,038

INTEGRAL JOINT DRILL PIPE Filed Feb. 23. 1939 INVENTOR Herber'i W. Graham Patented June 17, 1941 UNITED STATES PATENT OFFICE 2,246,038 m'rEGaAL JOINT mum. PIPE Herbert W. Graham, Pittsburgh, Pa., assignor to Jones & Laughlin Steel Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Application February 23, 1939, Serial No. 257,885

3 Claims.

This invention relates to integral joint drill pipe and the manufacture thereof. Such drill pipe is ordinarily formed by upsetting and each section has threaded ends whereby adjacent sections may be screwed directly together without the use of separate couplings. One form of in-. tegral joint drill pipe and one way of upsetting th same are disclosed, for example, in Patent No. 2,065,595.

Drill pipe is used for the rotary drilling of wells, such, for example, as oil wells, during which drilling the pipe is simultaneously rotated and advanced into the earth. The exterior of the pipe is subjected to severe wear and abrasion. Integral joint drill pipe as above referred to has outwardly projecting shoulders adjacent its ends, which shoulders are peculiarly subjected to wear and abrasion in service. Wear at the shoulders particularly limits the service life of the pipe, as the elevators which grip the pipe and lift it vertically out of the hole engage the pipe at the shoulders and when the shoulders become worn the elevators slip and jam, causing delays and handicapping drilling.

The resistance of drill pipe to wear and abrasion can be increased by hardening the same. However, from the practical standpoint the degree of hardness is limited, as great hardness is accompanied by brittleness, which may result in susceptibility to breakage due to impact. Great hardness of drill pipe also is objectionable to oil field workers whose tongs, which are used for tightening the sections together, slip and fail to hold when the steel of the drill pipe is very hard.

Due to the factors above mentioned the upper practical limit of hardness at the shoulders of drill pipe is in the neighborhood of 550 Brinell. The minimum hardness desirable is determined by wear characteristics and is found to be in the neighborhood of 375 Brinell.

Drill pipe made to the American Petroleum Institute specifications, which is employed in rotary well drilling, seldom exceeds a hardness about 225 Brinell in the normalized state. It i extremely diflicult, if not impossible, from the practical standpoint, to obtain the degree of.

practical to harden merely the surface of the pipe by the ordinary methods of case hardening, nitriding, etc., as these methods, besides being expensive, produce a relatively thin hardened zone which wears through unless made excessively hard, in which case the very hard skin tends to crack or spall oil under impact and also is undesirable for tonging, as explained above.

The most successful integral joint drill pipe is now made from a low carbon intermediate manganese steel with or without a small molybdenum content. For example, a steel containing not over about carbon and preferably between about .22% and about 32% .carbon and between about 1 and about 3% manganese is very satisfactory and has been adopted as a standard steel for the manufacture of integral joint drill pipe. .Such a low carbon intermediate manganese steel with the addition of molybdenum up to not over about A. has also been found highly satisfactory. In the steels above mentioned the phosphorus and sulphur contents are within normal ranges. These steels can be hardened in air to a Brinell-hardness of between 225 and 300 while retaining an impact toughness of not less than 30 foot pounds, Izod value. However, this hardness is considerably less than is desirable at the exterior of the shoulders of integral joint drill pipe where the heavy wear and abrasion occur in service, as above explained. It has been generally considered that steel having a manganese content as high as 2 or 2 particularly a low carbon steel, could not be quench hardened without cracking or warping.

I have discovered that it is possible to harden drill pipe so that the outer surface thereof at the shoulders is brought within the desired hardness range without any deleterious or undesirable effect on the pipe. Indeed I find that when drill pipe is hardened in accordance with my discovdry it is greatly improved \in structure and exhibits superior strength. I preferably flame harden the pipe as will be hereinafter explained. By so doing I obtain a hardness at the outer surface of the section at the shoulders of between about 375 and about 550 Brinell, the depth of the hardened zone being not over about /g".

it retains its toughness and ductility to the desired e tent. The hardness of such inner surface ll not ordinarily exceed about 350-Brinell. Intermediate the hardened outer surface and 'section of integral jointupset drill pipe.

the relatively soft and tough inner surface is a zone of transition which bonds together the inner and outer portions of the metal, and I find that there is no substantial tendency for the hardened outer portion of the metal to crack or spall off. Thus there is produced an outer layer of sufficient hardness to reduce wear to the desired extent and thick enough to obviate the danger of its being worn through before the pipe has otherwise reached the end of its usefulness. The tough and comparatively soft core provides adequate impact resistance and the transition zone insures against the cracking or spalling off of the hardened outer layer. The characteristics of the transition zone change gradually across such zone from those of the relatively hard wear resisting outer zone to those of the relatively tough shock resisting inner zone. The depth of the transition zone-that is, its dimension radially of the pipe-is generally in the neighborhood of one-fifth that of the outer hardened zone.

Other details, objects and advantages of the invention will become apparent as the following description of a present preferred embodiment thereof and a present preferred method present preferred embodiment of the invention and have illustrated a. present preferred method of practicing the same, in which Figure 1 is a central longitudinal cross-sectional viewthrough an end of a section of integral joint drill pipeshowing the same in position relatively to a multiple jet torch for flame hardening the outer surface of the section at its shoulder; and

Figure 2 is an end view of the pipe section and torch, showing also the quenching means.

Referring now more particularly to the drawing, reference numeral 2 designates generally a Such drill pipe may, for example, be upset as disclosed in Patent No. 2,065,595 and has a plain central portion 3, an upset box end 4 and an upset pin end at its opposite extremity (not shown), the box end being internally threaded as shown at 5 and the pin end being externally threaded to enable the same to be screwed into the box end of an identical drill pipe section.

My flame hardening process. about to be'de scribed may be and preferably is applied to both ends of the drill pipe section, but as the manner of application thereof to both ends is the same I have shown in the drawing only the box end and will describe the invention as applied to the flame hardening thereof, it being understood that;i the pin end may be similarly flame hardene The drill pipe section has an outwardly projecting shoulder 6. adjacent its end and the outer surface of the pipe at and adjacent such shoulder is flame hardened, as will now be described. The pipe section is mounted in chucks for rotation about its axis, one of the chucks being shown in dot and dash lines at I. Mounted adjacent the pipe section is a torch 8, which may, for example, employ a mixture of oxygen and acetylene to produce a flame of the desired temperature. The torch has suitable oxygen and acetylene inlet pipes 9 and a, plurality of jets. or tips i0 spaced along the torch generally in the direction of the length of the pipe. The oxygen and acetylene may be mixed in the torch 8 or in the tips, the gases emerging from the tips l0 and being ignited so as to burn with a series of flames spaced generally lengthwise of the pipe section and directed thereagainst so as to heat the outer surface of the metal of the section at and adjacent the shoulder 6.

The pipe section is slowly rotated in the direction of the arrow A in Figure 2. The speed of rotation is preferably such that a point on the outside surface of the section opposite the torch moves at'a speed of from about 5" to about 8'' per minute. The temperature of the flames where they impinge on' the outer surface of the section depends upon the speed of rotation and the particular steel being treated. For a steel having about 27% carbon and about 2.5% manganese, with the phosphorus and sulphur being held as low as possible; which is desirable in a steel of this type, and with the pipe rotating at a, surface speed of about 6" per minute, the steel is preferably heated to about 1440 F.

The quenching medium is introduced through one or more pipes H shown in Figure 2, such pipes preferably being spaced along the drill pipe section being treated generally in the direction of its length. They deliver the quenching medium to the heated outer surface of the pipe soon after it has been heated by the torch. The heat treatment is thus progressive about the pipe. It is being continuously heated and quenched so that the hardened zone gradually grows peripherally of the pipe. One complete revolution of the pipe is suflicient to effect the desired hardening, although the process may be varied if desired. The pipe may, on the other hand, be heated throughout its entire periphery and then quenched, and I find this procedure to be quite satisfactory. Instead of employing an elongated torch with a series of tips as shown I may employ a single torch mounted to travel generally lengthwise of the pipe and accomplish the heat treatment progressively both circumferentially and axially of the pipe. This, however, requires a very much longer time and is less satisfactory than the method above described employing an elongated torch with a plurality of jets or tips.

The area to be heat treated may be varied, although it is preferred to harden at least the inclined shoulder 6. In the drawing the hardened zone is indicated between the outer surface of the pipe and the dotted line i2. In the particular embodiment shown the heat treatment was extended a considerable distance beyond the shoulder toward the end of the pipe section and a short distance beyond the shoulder toward the center of the pipe section.

The torch tips or jets are preferably arranged equidistant tom the surface of the pipe as shown. Due to the varying diameter of the pipe the torch has an inclined portion opposite the shoulder 6 so that all of the tips will be equidistant from the surface during operation. The particular torch head shown is divided into two sections, each having its oxygen and acetylene inlet pipes, although this construction is not essential. It is to be understood, of course, that suitable pressure control and other necessa y equipment for operating the torch is provided. The acetylene and oxygen consumption per hour ranges between about 3 and about 30 cubic feet. depending on the other variables.

The quenching medium, which is introduced through the pipes ll, may be, for example, compressed air or water. If water is employed it will ordinarily be conducted directly to the surface of the pipe and will run down the pipe surface into a suitable run-ofl conduit so that it may be cooled and recirculated if desired. If air is employed as a quenching medium it is preferably supplied at a pressure of from 1 to 15 pounds per square inch above atmospheric pressure. The hardness can be controlled by controlling the temperature to which the outer surface of the metal is raised, the speed of rotation of the pipe and the character and temperature of the quenching medium. I have no difliculty hardening the .outer surface of the metal to between about 375 and about 550 Brinell and I find that greater hardness can be imparted to the metal if desired. For my purpose in the hardening of drill pipe a hardness substantially higher than 550 Brinell is not ordinarily desired. The depth of the hardened zone varies as above mentioned up to'about /2", the normal range being fromabout .025" to about .35" with the average being in the neighborhood of about A," to about A".

The heating medium may be constituted by gases other than oxygen and acetylene, or nongaseous heating means may be employed. I have found that heating by electrical induction is satisfactory, although at present gas heating is preferred.

While I have shown and described a present preferred embodiment of the invention and a present preferred method of practicing the same, it is to be distinctly. understood that the same is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.

I claim:

1. An integral joint drill pipe section of metal having aBrinell hardness of between about 175 and about 300, the section having an outwardly projecting shoulder adjacent an end thereof, the metal at the outer surface of thesection at said 10 shoulder having a Brinell hardness of between l5 projecting shoulder adjacent an end thereof, the

metal at the outer surface of the section at said shoulder having for a depth of not over about /2" a Brinell hardness of between about 375 and about 550.

3'. An integral joint drill pipe section of steel having a carbon content not substantially higher than about and a manganese content between 1 /4% and about 3% and having a Brinell hardness of between about 175 and about 300,

25 the section having an outwardly projecting shoulder adjacent an end thereof, the metal at the outer surface of the section at said shoulder having a Brinell hardness of between about 375 and about 550.

HERBERT W. GRAHAM. 

